The present invention relates to power generation systems, and more particularly relates to a hybrid combustion power system including multiple direct energy conversion devices.
An advantage of simple cycle steam turbine power plants is the ability to burn a wide variety of fossil fuels with relatively minor preconditioning. However, the efficiency of steam plants is limited despite the availability of high temperatures in their fossil fuel burners. A combined gas-steam cycle provides high efficiency, but burns natural gas which is relatively expensive. Utilization of less expensive fuels such as coal requires heavy preconditioning, e.g., integrated gasification combined cycle (IGCC) and pressurized fluidized bed combustion (PFBC), and lowers the overall plant efficiency.
An alternative to IGCC and PFBC technologies would be to use a direct energy conversion topping cycle which has no moving parts and can accept almost any type of fuel. However, direct energy conversion methods have relatively narrow ranges of heat source and heat sink temperatures to achieve efficient operation while ensuring sufficient lifetime and reliability.
In accordance with the present invention, a hybrid combustion power system comprising multiple direct energy conversion devices is provided. The conversion efficiencies of topping cycles and stand alone power systems are significantly increased by operating the direct energy conversion devices of the system efficiency and reliably at variable heat source and heat sink temperatures.
An aspect of the invention is to provide a hybrid combustion power system including a source of combustion air, a low temperature direct energy conversion device for heating the combustion air, and a high temperature direct energy conversion device for further heating the combustion air.
A further aspect of the invention is to provide a hybrid combustion power system comprising: a source of combustion air, combustion fuel, and coolant; at least one direct energy thermionic converter power generator for heating at least one of the combustion air and coolant; and a steam turbine to which any heated coolant passes.
Another aspect of the invention is to provide an alkali metal thermoelectric converter (AMTEC) having a parallel condenser system comprising: multiple opposing high temperature working fluid regions separated from each other by at least one vapor chamber; and multiple opposing low temperature coolant regions separated from each other by the at least one vapor chamber, and separated from the high temperature working fluid regions by insulating walls. The primary feature of AMTEC is its ability to generate electric power using the temperature difference between a hot stream and a cold stream. The hot stream is cooled as a side effect of the electric conversion process, and the cold stream is heated by waste heat from the AMTEC device. In different parts of this disclosure, some of the waste heat is used to heat combustion air, and some is used to heat feedwater and steam.
These and other aspects of the present invention will be more apparent from the following description.